Luminaires having a light emitting globular optical element or diffuser generally comprise a hollow globular shell having a light source disposed within the shell. This is an acceptable arrangement for illumination purposes. However, for ornamental purposes where brilliance and sparkle are desired, a solid (i.e., without cavities or voids) optical element is preferred. A relatively high index of refraction that is comparable to that of glass (typically about 1.6 to 1.9) is desired. For example, leaded crystal glass (having a lead content of about 24%) has an index of refraction of about 1.9, and consequently can be used to produce brilliant, sparkling ornamental lighting. However, the high density of leaded crystal glass (about 6.6 grams per cubic centimeter) can make it unsuitable for certain applications, such as ornamental street or other outdoor lighting applications. Further, casting of larger optical elements, such as for ornamental street lighting, would involve difficult processes and expensive tools, making glass optical elements impractical for most municipal park and other street lighting applications.